In recent years, for example, as a communication interface through which image or audio data is transmitted from a source device to a sink device at a high speed, a mobile high-definition link (MHL) standard is proposed (for example, see PTL 1). The MHL standard is an interface standard for high-speed video transmission to a mobile device.
In the MHL standard, power of +5 V for charging a battery is supplied from the sink device to the source device through a VBUS line. A current which can be drawn by the source device from the VBUS line varies depending on current supply capability of the sink device. The source device reads the capability of the sink device in advance, ascertains the current supply capability of the sink device, and thus, it is possible to utilize the upper limit current supply capability of the sink device for charging.